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DETERMINATION OF MOLECULAR WEIGHT

Example—Ten c.c. of benzene were used and two pellets of
naphthalene were added.
W.

IV.

0-2072
0*2072

874
874

d.
0-483
0-485

Af.
131-1
127-6

Mean.
} 129-3

Dynamical Method.—A third, somewhat different and
less accurate, method for determining the boiling-point is one
devised by Sakurai and
modified by Lands-
berger and later by
Walker and Lumsden.
The apparatus of
Walker and Lumsden
is shown in Fig. 34,
and consists of three
vessels, a boiling flask,
A, a tube, B, graduated,
in c.c. and an outer
jacket of glass, c. The
boiling flask is pro-
vided with a safety
tube, D, and a bent
tube, E, which is con-
nected with another
bent tube, F, passing
through a cork to the
bottom of the gradu-
ated tube, B. A ther-
mometer graduated in
tenths is inserted
through a second hole
in the same cork. There is a small hole at G in the graduated
tube below the cork through which the vapour of the boiling liquid
escapes into the outside jacket, and is condensed by a condenser
not shown in the diagram. The outer jacket, c, is attached by a
cork surrounding B. A small quantity of solvent (5—10 c.c.) is in-
troduced into the tube B and a larger quantity of the same solvent
into the boiling flask, A. The vapour from A passes into B and
raises it to the boiling-point, which is read off. The excess
of liquid which has condensed is poured out The weighed .

FIG. 33.

^Jt